PROGRAMMING

5.4BIT INSTRUCTIONS

A bit instruction addresses a specific bit in a memory location or SFR. There are four categories of bit instructions:

•SETB (Set Bit), CLR (Clear Bit), CPL (Complement Bit). These instructions can set, clear or complement any addressable bit.

•ANL (And Logical), ANL/ (And Logical Complement), ORL (OR Logical), ORL/ (Or Logical Complement). These instructions allow ANDing and ORing of any addressable bit or its complement with the CY flag.

•MOV (Move) instructions transfer any addressable bit to the carry (CY) bit or vice versa.

•Bit-conditional jump instructions execute a jump if the bit has a specified state. The bit- conditional jump instructions are classified with the control instructions and are described in section 5.5.2, “Conditional Jumps.”

5.4.1Bit Addressing

The bits that can be individually addressed are in the on-chip RAM and the SFRs (Table 5-5). The bit instructions that are unique to the MCS 251 architecture can address a wider range of bits than the instructions from the MCS 51 architecture.

There are some differences in the way the instructions from the two architectures address bits. In the MCS 51 architecture, a bit (denoted by bit51) can be specified in terms of its location within a certain register, or it can be specified by a bit address in the range 00H–7FH. The MCS 251 architecture does not have bit addresses as such. A bit can be addressed by name or by its location within a certain register, but not by a bit address.

Table 5-6 illustrates bit addressing in the two architectures by using two sample bits:

•RAMBIT is bit 5 in RAMREG, which is location 23H. “RAMBIT” and “RAMREG” are assumed to be defined in user code.

•IT1 is bit 2 in TCON, which is an SFR at location 88H.

Table 5-5. Bit-addressable Locations

Architecture

 

Bit-addressable Locations

 

 

 

On-chip RAM

 

SFRs

 

 

 

 

 

 

MCS® 251 Architecture

20H–7FH

 

All defined SFRs

MCS 51 Architecture

20H–2FH

 

SFRs with addresses ending in 0H or 8H:

 

80H, 88H, 90H, 98H, ..., F8H

 

 

 

 

 

 

 

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Intel 8XC251SB, 8XC251SA, 8XC251SP manual BIT Instructions, Bit Addressing, Architecture Bit-addressable Locations, SFRs
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Embedded Microcontroller, 8XC251SP, 8XC251SA, 8XC251SQ, 8XC251SB specifications

The Intel 8XC251 series of embedded microcontrollers is a family of versatile and powerful devices, designed to meet the demands of a wide range of applications. With models such as the 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP, this series offers unique features while maintaining a high level of performance and reliability.

At the heart of the 8XC251 microcontrollers is the 8051 architecture, which provides a 16-bit processor capable of executing complex instructions efficiently. This architecture not only allows for a rich instruction set but also facilitates programming in assembly language and higher-level languages like C, which are essential for developing sophisticated embedded systems.

One of the significant features of the 8XC251 family is its integrated peripherals, including timer/counters, serial communication interfaces, and interrupt systems. These peripherals enable developers to implement timing functions, data communication, and real-time processing, all of which are crucial in modern embedded applications. The 8XC251SB and 8XC251SQ models, for instance, come equipped with multiple I/O ports that allow for interfacing with other devices and systems, enhancing their functionality in various environments.

The memory architecture of the 8XC251 devices is noteworthy, featuring on-chip ROM, RAM, and EEPROM. The on-chip memory allows for fast access times, which is essential for executing programs efficiently. Moreover, the EEPROM serves as non-volatile memory, enabling the storage of configuration settings and important data that must be retained even when power is lost.

In terms of operating voltage, the 8XC251 devices are designed to operate in a wide range, typically between 4.0V and 6.0V. This flexibility makes them suitable for battery-powered applications, where energy efficiency is critical. The power management features, including reduced power modes, further enhance their suitability for portable devices.

Lastly, the 8XC251 series is supported by a wide range of development tools and resources, allowing engineers and developers to streamline the development process. This support, combined with the microcontrollers' robust features, makes the Intel 8XC251 family a reliable choice for various embedded applications, such as industrial automation, automotive systems, and consumer electronics.

Overall, the Intel 8XC251SB, 8XC251SQ, 8XC251SA, and 8XC251SP deliver high performance, versatility, and ease of use, making them a preferred choice for embedded system designers looking to develop efficient and effective solutions.
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